Technical Abstract:
Commercialization of guayule for producing latex for medical products and other uses is underway. As commercialization reaches full scale, the liquid waste stream from latex extraction will potentially become an increasing problem. The objectives of this study were to evaluate the properties of the liquid waste stream after latex extraction and determine whether any or all of the waste liquid could be recycled for latex extraction before disposal.
Waste liquid was collected from three waste stream sources in a latex extraction facility. Currently, wastes from all three sources are discharged from the facility. Each of the three sources was analyzed for Na, K, Ca, Mg, SAR, and pH. Based on these analyses, six treatments were developed for recycling two of the waste streams. Treatment 1 was a control using 100% original/new antioxidant solution for each extraction. Treatment 2 was a mixture of 70% original and 30% waste stream #3. Treatment 3 was a mixture of 50% original, 30% waste stream #3, and 20% waste stream #2. Treatment 4 was a mixture of 20% original, 30% waste stream #3, and 50% waste stream #2. Treatment 5 was 100% waste stream #2. Treatment 6 was 100% waste stream #3. All mixtures are based on the volume percent of the final mixture. After the mixtures for the treatments were made, each was analyzed for Na, K, Ca, Mg, SAR, C, N, and pH. The treatments were used as the antioxidant solution in the laboratory latex extraction process of freshly chipped guayule shrub. Each treatment was replicated four times in a completely randomized design. Following latex extraction, the homogenate from each sample was analyzed for Na, K, Ca, Mg, SAR, EC, C, and N. The total latex extracted was also determined.
Results showed that using any of the treatments to recycle waste liquid resulted in a lower SAR of the waste being discharged (26.95 to 10.5). The N content of the waste liquid averaged about 0.2% and could be recaptured as fertilizer. The K values were also high (500-600 ppm), indicating that guayule probably has a high K requirement and may require extra K fertilizer especially where soil tests are low in K. The solids in the waste stream and the obnoxious odor characteristic of the waste liquid could be overcome by lowering the pH of the waste liquid from over 10 to less than 7. If this were done with phosphoric acid, then the waste solids would be high in N, P, and K and could be an acceptable fertilizer for plant use. The best treatment for latex extraction was Treatment 4 with an increase of 2.4x the amount of latex extracted than the control (Treatment 1). This increase is probably due to recovery of latex from the waste liquid rather than increased extraction from the shrub as indicated by similar changes in SAR values between the treatments.
The waste liquid obtained during latex extraction can be recycled for latex extraction, thus reducing the amount of waste liquid discharged by about 50%. The waste that is discharged should be of value for use as a fertilizer.